Vladimir Putin has denied having any links to offshore accounts and described the Panama Papers document leaks scandal as part of a US-led plot to weaken Russia.

Mr Putin also defended a cellist friend named as the alleged owner of an offshore company, describing him as a philanthropist who spent his own funds to buy rare musical instruments for Russian state collections.

Speaking at a media forum in St Petersburg, Mr Putin said Western media pushed the claims of his involvement in offshore businesses even though his name did not feature in any of the documents leaked from a Panamanian law firm.

Mr Putin described the allegations as part of the US-led disinformation campaign waged against Russia in order to weaken its government. "They are trying to destabilise us from within in order to make us more compliant," he said.

"I would reject the premise or the assertion that we're in any way involved in the actual leak of these documents," US State Department spokesman Mark Toner told reporters in Washington.

The Washington-based International Consortium of Investigative Journalists (ICIJ) said the documents it obtained indicated that Russian cellist Sergei Roldugin acted as a front man for a network of Putin loyalists, and, perhaps, the president himself.

The ICIJ said the documents show how complex offshore financial deals channelled as much as 2 billion dollars to a network of people linked to the Russian president.

Mr Putin said Mr Roldugin, a long-time friend, did nothing wrong. He said he was proud of Mr Roldugin, adding that the musician spent his personal money to advance cultural projects.

Mr Roldugin used the money he earned as a minority shareholder of a Russian company to buy rare musical instruments abroad and hand them over to the Russian state, Mr Putin said.

"Without publicising himself, he also has worked to organise concerts, promote Russian culture abroad and effectively paid his own money for that," Mr Putin added. "The more people like him we have, the better. And I'm proud to have friends like him."

Mr Putin contended that Washington has fanned allegations of Russian official corruption in order to weaken Moscow as the US has become concerned about Russia's growing economic and military might.

"The events in Syria have demonstrated Russia's capability to solve problems far away from its borders," he said, adding that Moscow has achieved its goal "to strengthen the Syrian statehood, its legitimate government bodies."

Mr Putin said it is essential to prevent the collapse of the Syrian state to stem the flow of refugees to Europe.

He praised cooperation between Moscow and Washington in efforts to broker a ceasefire, which went into effect on February 27. The truce excludes the Islamic State group and the al Qaida branch known as the Nusra Front.

But while lauding contacts on Syria, he signalled tensions on another issue, accusing the US of breaching its obligations under an agreement to reprocess weapons-grade plutonium.

He said that while Russia has abided by the deal and built reprocessing facilities, the US has opted for a different technology which, he alleged, allowed it to maintain the so-called "return potential" of keeping weapons-grade materials if it wishes to do so.

Mr Putin said a rift over the issue was one of the reasons behind his decision to snub a nuclear summit hosted by US President Barack Obama in Washington.